Yaoi w/ seme jacking off on uke and ejaculates on uke while uke is asleep?

Sounds like you thing for somnophilia...
you can find some on these:
http://www.mangago.zone/tag/Somnophilia/
https://myreadingmanga.info/tag/somnophilia/
https://nhentai.net/search/?q=sleeping+males+only+english

*have a thing

http://www.mangago.zone/read-manga/k_s_secret/uu/d_chapter-11/pg-1/

i remember reading one where they're step brothers and the seme aka older brother is really and i mean really into the uke but i can't remember the name of it. I'll try to find it tho

i found it http://www.mangago.zone/read-manga/fubin_bl/

Color recipe, but its not really shown, just hinted at.

Totsuzen, Doukyonin ni Marking Saremashita